Steering shafts for motor vehicle steering units with electrical or electromechanical support of auxiliary forces are basically known. The steering shafts exhibit an input shaft, which is connected to the steering wheel, which in turn the driver of a motor vehicle uses to introduce a steering torque as a steering command to the motor vehicle steering unit. An output shaft connected to an input shaft is foreseen to transfer the steering torque via tie rods to the wheels to be steered. In order to determine the supporting force needed in each case for an electrical or electromechanical auxiliary force support connected to the output shaft, the input and output shafts are typically elastically connected to each other by a torsion bar and the torque introduced by the driver onto the input shaft can be determined by measuring the relative torsion between the input and output shafts.
Auxiliary force supports, for example electrical or electromechanical auxiliary force supports, are used to introduce the corresponding auxiliary torques typically onto the output shaft, the steering pinion or the rack. In this way the respective auxiliary force support is driven with regards to the output shaft through the determination of the torque introduced by the driver onto the input shaft using the steering wheel.
It is known for electromechanical auxiliary force supports in motor vehicle steering units that the respective supporting force is introduced by an electrical motor, whereby the supporting force is, for example, transferred via a driving worm onto a worm wheel, which is connected to the steering train. To this purpose the electrical motor is typically connected to the driving worm, either through a direct positioning of the driving worm onto the output shaft of the electrical motor, or through a gear that is positioned between the electrical motor and the driving worm. The driving worm acts on a worm wheel, which transfers the torque, for example, via a gear, a rack-and-pinion mechanism or a belt drive onto the specific steering train. In this way the auxiliary force support can introduce the supporting force, for example, in the area of the steering shaft, the steering pinion or the steering rack.
The driving worm is normally enclosed in a housing of the apparatus using a roller bearing. In order to provide for an angle compensation in the bearing position, through which, for example, installation tolerances or a bending of the driving worm due to the arising radial forces, which can result from a slight deflection of the driving worm, can be compensated for, compensation and suspension mechanisms can be used. As a result of the angle compensation achieved in this way, the roller bearing can be operated such that only radial components need to be supported whereby the noise level is reduced.
In EP 2 423 075 A2, an electrical steering fixture is described, by which a bearing supporting the driving worm is arranged between the roller bearing and the housing of the auxiliary force support using a spring ring, which exhibits leaf spring elements. As a result the bearing is adjustable in all directions and a defined pivoting axis for an angle compensation is not provided for.